The Lake Fire continued to burn overnight in the San Bernardino Mountains and has grown to 29,813 acres - making it the third-largest wildfire in the region in the past 10 years.

It surpassed the Mountain Fire, which burned 27,531 acres near Idyllwild in July 2013. The Lake Fire is third in size behind the 2006 Sawtooth Complex Fire, which burned 70,000 acres near Pioneertown, and the Esperanza Fire, which charred 40,000 acres near Banning just a few months later.

As of 8 a.m. Friday, firefighters had contained 19 percent of the Lake Fire and the cost of battling it was $17.6 million, according to the U.S. Forest Service.

The fire is threatening 7,390 buildings. Through Thursday night, the Forest Service had been reporting 500 buildings were threatened.

Officials have not determined what sparked the fire, but "I doubt it was lightning-caused," said Tom Rolinski, a meteorologist with the Forest Service.

The fire began growing significantly Wednesday after a drone was spotted in the area. That forced officials to ground their aircraft for several hours, allowing flames to spread.

"It's not just the fact that it shut us down -- the fire certainly grew," forest aviation officer Mike Eaton said during a news conference at the San Bernardino Forest Airtanker Base on Thursday.

The fire's expansion reduced containment, which dropped from 27 percent Wednesday night to 21 percent Thursday morning and again to 19 percent that evening.

Eaton, who was in the air on Wednesday when the drone was discovered, is in charge of aviation operations in the San Bernardino and Cleveland national forests.

The effects of the lost time could be compounded by the fact that flames could slip through the untreated terrain.

"We weren't able to complete the line that we were working on so we had gaps in the retardant, so the fire is going to progress through the retardant, possibly," Eaton said.

Eaton stood near the tarmac at the airbase as he described the chain of events in front of a bank of TV cameras and a large crowd of reporters. Fire officials gathered the media together to get the word out: "If you fly, we can't."

About 5:30 p.m. Wednesday, one of the air tactical group supervisors over the incident encountered a drone – which Eaton also referred to as a UAV (Unmanned Aerial Vehicle) or UAS (Unmanned Aircraft Systems). All refer to an aircraft with no pilot.

The drone passed between an aircraft flying at 11,500 feet – and a lead plane at 10,500 feet – at a 500-foot separation.

"Not a near miss with respect to an incident, but certainly an aircraft in our airspace we were not prepared for," Eaton said. "Not having communications with that aircraft, we shut down our fixed-wing operation. We were working the south side of the Lake Fire near San Gorgonio peak at very high altitudes."

Rimrock resident Bert Franklin, who was among those evacuated early Thursday due to their proximity to the fire, said he noticed Wednesday that aircraft weren't battling the fire. Shortly after, he said smoke from the fire grew.

On Thursday, he heard about the drone and suspected there could be a connection.

"It would make you wonder if that's what poofed up the fire," said Franklin, 75. "That's a major problem."

Eaton described the drone as orange or red in color with about a four-foot wingspan. It was illegally flying in Temporary Flight Restricted Airspace.

"We're not able to track the aircraft back to its source or whoever was controlling it," he said. "With that, we shut the aircraft down for the rest of the day – it limited our ability to fight the fire."

Aircraft could be seen dropping retardant on the fire on Thursday. By that point, smoke had grown into a gigantic plume and it could be seen for miles across the High Desert and Coachella Valley.

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(Photo: Colin Atagi/The Desert Sun)

As the blaze strengthened, law enforcement officials ordered residents living north of Pioneertown to evacuate early Thursday. Burns Canyon resident Gary Alger, 68, said officials alerted residents about 1 a.m. and he left home at 5 a.m. after grabbing important legal documents, clothes and metal detectors.

Hours later, he was among the residents gathered outside Pappy & Harriet's, where firefighters set up a makeshift informational station in Pioneertown.

"Hell's yes, I'm worried," Alger said.

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(Photo: Colin Atagi/The Desert Sun)

The atmosphere in and near Pioneertown has changed significantly over the past week.

Just two days after the June 17 fire began and as a thick layer of smoke covered the High Desert, residents had little concern about the fire and most people went about their daily business.

On Thursday, fire trucks were scattered everywhere and at least five cars parked outside Pappy & Harriet's at any given time. People were rushing to the information station for the latest updates while others sought details from the waiting firefighters.

Burns Canyon and Rimrock are under mandatory evacuations and Pioneertown is under a voluntary evacuation. Thursday, the San Bernardino County Sheriff warned residents in the Lake Williams, Erwin Lake and Lake Baldwin area to prepare to evacuate if it becomes necessary. As of 6:30 p.m., the fire was 1.5 miles east of the first predestined point set up by fire officials to determine when evacuation is necessary.

An evacuation center is set up at Copper Mountain Community College in Joshua Tree and people may drop off pets at the Yucca Valley Animal Shelter or Yucca Valley Equestrian Center.

There were no evacuees at the college Thursday morning, although campus officials said they've received phone calls from residents inquiring about the evacuation center.

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Stringbean is dropped off at the Yucca Valley Equestrian Center Thursday. At least 20 horses were left there while owners evacuate due to the Lake Fire.(Photo: Colin Atagi/The Desert Sun)

Only one dog was checked into the animal shelter, but at least 20 horses and three goats were taken to the equestrian center.

Pioneertown resident Kim Shaw brought six horses to the equestrian center as a precaution, since it would allow her and her husband to more easily evacuate if necessary.

"They're safe here. I don't have to worry about them," said Shaw, 53. "They think they're on a vacation."

Officials say the Lake Fire, which was reported about 4 p.m. June 17, could burn for another week.

The cost of battling the Lake Fire is nearing $15 million, according to the U.S. Forest Service.

It's the largest of five wildfires in California and was quickly on track to becoming the third-largest fire near the High Desert or Coachella Valley in the past decade.

The 2006 Sawtooth Complex Fire is the largest, having burned 70,000 acres near Yucca Valley and Pioneertown. It was followed months later by the Esperanza Fire, which charred 40,000 acres near Banning and killed five U.S. Forest Service firefighters.

The other two fires were the Mountain Fire, which burned 27,531 acres near Idyllwild in 2013, and the Silver Fire, which burned 20,292 acres near Banning that same year.

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Firefighters parked at the end of Burns Canyon Road in Rimrock, Thursday, where they are monitoring the Lake Fire in the San Bernardino Mountains.(Photo: Colin Atagi/The Desert Sun)

Burns Canyon resident Bill Yancey lost his home during the Sawtooth Fire. It took him two years to rebuild, and he was again evacuated early Thursday because of the Lake Fire.

He was with those waiting outside Pappy & Harriet's and his car was filled with clothes, guitars and his dog.

"I was ready to go last Wednesday," Yancey said.

He went to the evacuation center, but he left after he saw no one was there. He returned to Pioneertown and said he planned to check on his home Thursday.

Firefighters estimated flames were two to five air miles from Rimrock. That translates to at least four to 10 land miles.

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A firetruck heads north on toward Rimrock and Burns Canyon in the High Desert. The communities were evacuated Thursday because of the Lake Fire.(Photo: Colin Atagi/The Desert Sun)

Several firefighters waited at the very tip of Burns Canyon Road, which ends at a private dirt road that stretches into the mountains. A fire official said they were monitoring the fire for now.

Meanwhile, news about the drone spread across the area. Alger said it made him mad.

Eaton referred to a famous aircraft mishap when describing some of the dangers inherent in flying in airspace with a drone.

"We had the flight that went down in New York, landed in the Hudson River, that was due to running into birds. This is no different than a bird. It could be made out of metal, aluminum, wood – but we don't want that going through our engines, going through our props, running into either our helicopters or fixed-wing airplanes."

Law enforcement has been posted in the area Thursday as well.

"Should we have another encounter – law enforcement will be in the area to hopefully see where it ends up, where its landing site is.

"We manage that airspace (over the Lake Fire) – the FAA requires any aircraft entering that air space to communicate with us," Eaton said.

"(It's) impairing an official in the administration of their duties – keeping us from fighting the fire. That's what it did … it kept us – just the aircraft we had in the air at the time - from delivering 5,000 gallons of retardant to the fire and any subsequent missions we might have had.

"We had to jettison those loads up in our jettison area – those loads didn't make it to the fire as expected. So, in real cost, in what we lost - yeah 5,000 gallons, $10,000 - $15,000 – that's not the big part of it. The big part of it is we had to shut down subsequent missions that could have contained – possibly – that south side of the fire."

Later on Wednesday, a helicopter-type drone was seen at an elevation of about 700 feet above the rim of Lake Arrowhead – just due north of the airtanker base.

Air operations resumed at 9 a.m. Thursday – an hour later than usually scheduled because planes were sent out to scout the area before the air tankers began their rotations.

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U.S. Forest Service spokesman John Miler at the San Bernardino National Forest Airtaner Base, Thursday, June 25, 2015.(Photo: Denise Goolsby/The Desert Sun)

"What this fire is showing us is this will not be a normal fire season – there is nothing normal about the way the fuels are burning and are being consumed," U.S. Forest Service spokesman John Miller said during the news conference. "We're seeing fire activity above 10,000 feet that we have not seen in many years. As a result of that, we're taking some additional preventative measures.

In addition to increasing presence eliminating all campfires within the San Bernardino National Forest, that's a move we haven't taken since 2003."